1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2023 Loongson Technology Corporation Limited
4 */
5
6 #include <linux/cpu.h>
7 #include <linux/init.h>
8 #include <asm/fpu.h>
9 #include <asm/smp.h>
10
11 static unsigned int euen_mask = CSR_EUEN_FPEN;
12
13 /*
14 * The critical section between kernel_fpu_begin() and kernel_fpu_end()
15 * is non-reentrant. It is the caller's responsibility to avoid reentrance.
16 * See drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.c as an example.
17 */
18 static DEFINE_PER_CPU(bool, in_kernel_fpu);
19 static DEFINE_PER_CPU(unsigned int, euen_current);
20
21 void kernel_fpu_begin(void)
22 {
23 unsigned int *euen_curr;
24
25 preempt_disable();
26
27 WARN_ON(this_cpu_read(in_kernel_fpu));
28
29 this_cpu_write(in_kernel_fpu, true);
30 euen_curr = this_cpu_ptr(&euen_current);
31
32 *euen_curr = csr_xchg32(euen_mask, euen_mask, LOONGARCH_CSR_EUEN);
33
34 #ifdef CONFIG_CPU_HAS_LASX
35 if (*euen_curr & CSR_EUEN_LASXEN)
36 _save_lasx(¤t->thread.fpu);
37 else
38 #endif
39 #ifdef CONFIG_CPU_HAS_LSX
40 if (*euen_curr & CSR_EUEN_LSXEN)
41 _save_lsx(¤t->thread.fpu);
42 else
43 #endif
44 if (*euen_curr & CSR_EUEN_FPEN)
45 _save_fp(¤t->thread.fpu);
46
47 write_fcsr(LOONGARCH_FCSR0, 0);
48 }
49 EXPORT_SYMBOL_GPL(kernel_fpu_begin);
50
51 void kernel_fpu_end(void)
52 {
53 unsigned int *euen_curr;
54
55 WARN_ON(!this_cpu_read(in_kernel_fpu));
56
57 euen_curr = this_cpu_ptr(&euen_current);
58
59 #ifdef CONFIG_CPU_HAS_LASX
60 if (*euen_curr & CSR_EUEN_LASXEN)
61 _restore_lasx(¤t->thread.fpu);
62 else
63 #endif
64 #ifdef CONFIG_CPU_HAS_LSX
65 if (*euen_curr & CSR_EUEN_LSXEN)
66 _restore_lsx(¤t->thread.fpu);
67 else
68 #endif
69 if (*euen_curr & CSR_EUEN_FPEN)
70 _restore_fp(¤t->thread.fpu);
71
72 *euen_curr = csr_xchg32(*euen_curr, euen_mask, LOONGARCH_CSR_EUEN);
73
74 this_cpu_write(in_kernel_fpu, false);
75
76 preempt_enable();
77 }
78 EXPORT_SYMBOL_GPL(kernel_fpu_end);
79
80 static int __init init_euen_mask(void)
81 {
82 if (cpu_has_lsx)
83 euen_mask |= CSR_EUEN_LSXEN;
84
85 if (cpu_has_lasx)
86 euen_mask |= CSR_EUEN_LASXEN;
87
88 return 0;
89 }
90 arch_initcall(init_euen_mask);
91
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